Synapses Flashcards

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1
Q

What is a synapse?

A

A physical gap between neurones

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2
Q

Impulses can only cross synapses in one direction. Explain why

A

Neurotransmitter only released from pre-synaptic knob
Receptors for neurotransitter only present on post-synaptic membrane

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3
Q

What is a cholinergic synapse?

A

Synapses that use acetylcholine

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4
Q

What happens to the neurotransmitter once attached to the receptors on the post-synaptic membrane?

A

Hydrolysed by an acetylcholinesterase
Forms acetyl and choline which diffuse back to pre-synaptic membrane.

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5
Q

What stimulates the synaptic vesicles to move towards the pre-synaptic membrane?

A
Calcium ion channel proteins open
Calcium ions (facilitated) diffuse into the synaptic knob
Calcium ions cause vesicles to move towards membrane
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6
Q

What happens when the acetylcholine binds with receptors on the

post-synaptic membrane

A

Sodium ion channels open
Sodium ions diffuse into the post-synaptic knob
If threshold is reached an action potential is generated

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7
Q

What is temporal summation?

A

Two or more nerve impulses arrive in quick succession from the same pre-synaptic membrane.
More neurotransmitter released
More sodium ions channels open on post synaptic membrane
Threshold more likely to be achieved.

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8
Q

What is spatial summation?

A

Many neurones connect to one neurone at a synapse
Each neurone releases small amounts of neurotransmitter
More sodium ions channels open on post synaptic membrane
Threshold more likely to be achieved

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9
Q

Describe how calcium ions are involved in synaptic transmission.

A

High concentration of calcium ions maintained in the synaptic cleft
Arrival of an action potential opens the calcium ion channels
Calcium ions enter pre-synaptic knob
Influx of calcium ions causes vesicles to move to pre-synaptic membrane and release acetylchoine into the synapse

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10
Q

GABA causes negatively charged chloride ions to enter the post synaptic neurone. How does this inhibit the propagation of an nerve impulse?

A

Neurone becomes more negatively/charged
More sodium ions need to diffuse into post synaptic knob to reach theshold
Depolarisation less likely to happen

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11
Q

How might drugs decrease synaptic transmission?

A

Decrease synthesis of neurotransmitter
Inhibit release of neurotransmitter
Decrease permeability of post synaptic membrane to ions
Increased activity of acetylcholinesterase
Block receptor sites on postsynaptic membrane
Hyperpolarise post synaptic membrane

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12
Q

How might drugs increase synaptic transmission?

A

Increased synthesis of neurotransmitter
Increases release of neurotransmitter f
Inhibit acetylcholnesterase
Mimic shape of neurotransmitter

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13
Q

How does the neurotransmitter cross the synaptic cleft/

A

Simple diffusion

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